It's "functional" but has too many caveats that make it a pain to use on a daily basis. Like, tabs don't update while in the background, it keeps killing tabs after some time, scrolling on some sites is a mess because the navbar gets fucked and starts covering half the page for some reason, when certain HTML elements are too close to a hyperlink you can't click on them, etc. These are all things that worked fine on version 68 and before.

I use FF on Android and don't suffer any of the things you mentioned and have used it on multi android versions on multi android devices.

I wonder if it's the amount of memory on my phone then. The thing is, the old version of FF didn't do this, and neither does the current version of Vivaldi.

How many tabs are you using?

Not that many.

But it's not something that I'm doing specifically for Firefox, my style is to close tabs after I'm finished with them.